This project is concerned with spinal cord development in anuran larvae (Rana catesbeiana tadpoles). Using electrophysiological and anatomical techniques, the neurons and neuronal connections developing to subserve behavior in the frog will be examined. Particular attention will be paid to the development of the lumbar lateral motor column, composed of hindlimb motoneurons. In addition to these developing neuronal networks, the tadpole spinal cord contains a system of neurons born in embryonic stages which do not persist in the same form into metamorphosis. An example of this more mature class of neurons is the primary motoneuron, which innervates swimming musculature and manifests rhythmic motor output in the in vitro spinal cord preparation. The interaction within the tadpole spinal cord of this differentiated class of neurons with deveolping neurons forms a second focus of this project.